"Clinically, our results highlight the importance of considering a possible role for loss of close personal relationships through death in assessment of psychiatric disorders. When someone loses a close personal relationship, even late in life, there is a profound effect on sense of self and self-reflection," lead author Katherine Keyes, an assistant professor of epidemiology at Columbia University's Mailman School of Public Health, said in a university news release.

"Even in adults with no history of psychiatric disorders, it is also a vulnerable risk period for the onset of a potentially disabling psychiatric disorder," Keyes added.

The study, published online recently in the American Journal of Psychiatry, involved more than 27,000 people. Of these participants, 20 percent to 30 percent said the sudden loss of a loved one was the most traumatic thing that ever happened to them. Even among those who reported facing 11 or more traumatic events, 22 percent said the unexpected loss of a loved one was the most traumatic experience.

The greatest increase in risk across all age groups was for PTSD. The researchers found as much as a 30-fold increase in the chances for this condition.

The sudden loss of a loved one also roughly doubled the risk for mania in people aged 30 and older. This was true even after the researchers took other factors into account such as medical history, other traumatic experiences, gender, race, income, education level and marital status.

This risk increased with age. The study revealed a fivefold increase in the risk for mania among those aged 50 and younger or 70 or older.

The sudden loss of a loved one is also linked to increased risk for other mental health issues such as: